Copolymerized starch composition

Abstract

Preformed, homogeneous, non-linear starch copolymerizate articles may be prepared by copolymerizing a preformed, homogeneous mixture of water, ethylenically unsaturated starch and ethylenically unsaturated monomers to provide a labyrinth of copolymerized starch chains interconnected with each other by the copolymerized monomeric units. The invention is particularly suitable for preparing high-binder, aqueous coating compositions which may be applied to a variety of substrates and subsequently copolymerized with polymerization initiating systems. Improved water- and detergent-resistance may be obtained by incorporating film-forming additives, cross-linking reagents or polyunsaturated compounds into the copolymerizable starch composition.

What is claimed is: 
     
       1. A copolymerizable, hydrophilic, film-forming, starch composition suitable for use in preparing articles which are coated with a starch copolymerizate, said starch composition comprising a homogeneous mixture of (a) water; (b) water-dispersible ethylenically unsaturated starch comprised of starch chains and appendant ethylenically unsaturated groups uniformly distributed throughout the starch with said appendant groups being individual monomeric condensates contiguously attached to starch chains at a degree of substitution of at least 0.001; and (c) water-dispersible, monoethylenically unsaturated monomer homogeneously dispersed throughout the starch composition in an amount sufficient to copolymerize with the ethylenically unsaturated appendant groups of the starch to provide a homogeneous copolymerizate of starch chains linked together by polymerized units of said monoethylenically unsaturated monomer and said appendant groups. 
     
     
       2. The starch composition according to claim 1 wherein the water-dispersible, ethylenically unsaturated starch comprises a starch represented by the formula: ##STR10## wherein Z represents a divalent organo group linking the terminal ethylenically unsaturated group to the starch chain, starch represents a starch chain, "a" represents a D.S. of greater than 0.01 and "R" is a member selected from the group consisting of hydrogen and a mono-organic radical. 
     
     
       3. The starch composition according to claim 2 wherein "a" has a value corresponding to a D.S. ranging from about 0.02 to less than 0.5, "R" is a member selected from the group consisting of hydrogen and a lower alkyl group, the appendant group has a molecular weight greater than 50 and less than 300, the starch chain comprises a starch hydrolyzate and the starch composition contains at least 5 to about 800 parts by weight water for each 100 parts by weight ethylenically unsaturated starch. 
     
     
       4. The starch composition according to claim 1 wherein the composition comprises from about 30 to about 500 parts by weight water and from about 10 to about 200 parts by weight ethylenically unsaturated monomer for each 100 parts by weight ethylenically unsaturated starch. 
     
     
       5. The composition according to claim 4 wherein the ethylenically unsaturated monomer provide a polymer having an average glass transition temperature of less than 80° C. when said monomer is polymerized. 
     
     
       6. The composition according to claim 5 wherein the water-dispersible ethylenically unsaturated monomer comprises at least one member selected from the group consisting of hydroxyalkyl acrylate and hydroxyalkyl methacrylate. 
     
     
       7. The composition according to claim 6 wherein the ethylenically unsaturated starch comprises a starch having an ethylenic unsaturation D.S. ranging from about 0.05 to about 0.2. 
     
     
       8. The composition according to claim 1 wherein the ethylenically unsaturated starch is characterized as containing monoethylenically unsaturated appendant groups having polar groups juxtapositioned to the monoethylenically unsaturation which activates the copolymerizability of the ethylenic unsaturated group of said appendant group when said starch composition is exposed to free-radical polymerization catalysis. 
     
     
       9. The composition according to claim 8 wherein the composition comprises an ethylenically unsaturated starch having an appendant group D.S. ranging from about 0.02 to about 0.3, water ranging from about 30 to about 500 parts by weight, ethylenically unsaturated monomer ranging from about 50 to about 500 parts by weight, and ethylenically unsaturated monomer characterized as providing a polymer having an average polymer glass transition temperature of less than 80° C. when said monomer is polymerized. 
     
     
       10. The composition according to claim 9 wherein the starch composition comprises an ethylenically unsaturated starch hydrolyzate which has an amylose content of less than 30% by weight, the starch composition has a Brookfield viscosity ranging from about 20 cps to about 500 cps and the starch composition contains free-radical polymerization initiator in an amount sufficient to permit the copolymerization of said ethylenically unsaturated starch with said ethylenically unsaturated monomer when said starch composition is exposed to polymerization initiating means to cause the generation of free-radicals within said starch composition. 
     
     
       11. The starch composition according to claim 1 wherein the ethylenically unsaturated starch consists essentially of a starch acrylamide represented by the formula: ##STR11## wherein starch represents a starch chain, R 1  is a member selected from the group consisting of hydrogen and a mono-organo group joined directly to the nitrogen atom by a monovalent bond, R represents a member selected from the group consisting of hydrogen and mono-organo group linked to the alpha carbon atom of the ethylenically unsaturated group of the acrylamide moiety by a monovalent linkage, Q represents an organo group which divalently joins the D group with the acrylamide group; D is a member selected from the group consisting of sulfur and oxygen linking said Q group to the starch chain and "a" represents the number of acrylamide substituents per anhydroglucose unit of said starch molecule. 
     
     
       12. The starch composition according to claim 11 wherein "a" represents a D.S. ranging from about 0.01 to about 0.5, "R" and "R 1  " represent a member selected from the group consisting of hydrogen and a lower alkyl group and the individual appendant groups are characterized as having a molecular weight greater than 50 but less than 300. 
     
     
       13. The starch composition according to claim 11 wherein the composition contains from about 25 to about 800 parts by weight water and from about 50 to about 500 parts by weight ethylenically unsaturated monomer for each 100 parts by weight unsaturated starch and D is an oxy group. 
     
     
       14. The composition according to claim 13 wherein the ethylenically unsaturated monomer provides a polymer having an average polymer glass transition temperature of less than 70° C. when said monomer is polymerized, and the composition contains latent polymerization initiator in an amount sufficient to copolymerize said ethylenically unsaturated starch with said ethylenically unsaturated monomer when said starch composition is exposed to polymerization initiating means to induce the copolymerization of said composition. 
     
     
       15. The composition according to claim 11 wherein the D.S. of starch acrylamide ranges from about 0.05 to about 0.3, the starch acrylamide comprises a starch acrylamide hydrolyzate and the starch composition contains a sufficient amount of hydrogen peroxide to copolymerize said ethylenically unsaturated monomer with said starch acrylamide when said starch composition is subjected to polymerization initiating means which is sufficient to cause said hydrogen peroxide to form free-radicals within said starch composition. 
     
     
       16. The starch composition according to claim 15 wherein D comprises an oxy group, the starch composition contains from about 25 to about 800 parts by weight water and about 50 to about 500 parts by weight monoethylenically unsaturated monomer for each 100 parts by weight starch acrylamide, and monoethylenically unsaturated monomer characterized as providing a polymer having an average polymer glass transition temperature of less than 70° C. when said monomer is polymerized. 
     
     
       17. The starch composition according to claim 16 wherein R 1  is hydrogen, R is a member selected from the group consisting of hydrogen and methyl group and Q is a methylene group. 
     
     
       18. The starch composition according to claim 17 wherein the starch acrylamide consists essentially of a starch acrylamide hydrolyzate and the starch composition has a viscosity ranging from about 20 cps to about 40,000 cps. 
     
     
       19. The starch composition according to claim 18 wherein the ethylenically unsaturated monomer comprise hydroxyalkyl acrylate. 
     
     
       20. The composition according to claim 17 wherein the starch composition contains at least one effective member selected from the group consisting of film-forming additive, cross-linking reagent and polyethylenically unsaturated compound with said member being present in said starch composition in an amount sufficient to improve the water-resistance of copolymerizates prepared from said starch composition. 
     
     
       21. The starch composition according to claim 20 wherein the amount of said member is sufficient to impart improved detergent-resistance properties to copolymerizates which are prepared from said starch composition. 
     
     
       22. The starch composition according to claim 1 wherein the water-resistance of films formed from said copolymerization of said starch composition is improved by incorporating into the starch composition at least one effective member selected from the group consisting of film-forming additive, cross-linking reagent and polyethylenically unsaturated compound with said member being present in said starch composition in an amount sufficient to impart improved water-resistance to copolymerizates of said starch composition. 
     
     
       23. The starch composition according to claim 22 wherein the amount of said member is sufficient to impart improved detergent-resistance properties to copolymerizates which are prepared from said starch composition. 
     
     
       24. A method for preparing a starch copolymerizate article which comprises the steps of: A. preforming a starch composition into a desired configuration with said starch composition comprising a homogeneous mixture of: (a) water;   (b) water-dispersible, ethylenically unsaturated starch comprised of starch chains and appendant ethylenically unsaturated groups uniformly distributed throughout the starch with said appendant groups being individual monomeric condensates contiguously attached to starch chains at a degree of substitution of at least 0.001;   (c) water-dispersible, monoethylenically unsaturated monomer homogeneously dispersed throughout the starch composition in an amount sufficient to copolymerize with the ethylenically unsaturated appendant groups of the starch to provide a homogeneous copolymerizate of starch chains linked together by polymerized units of said monoethylenically unsaturated monomer and said appendant groups;     B. copolymerizing the preformed starch composition article to a starch copolymerizate by exposing the preformed starch composition to polymerization initiating means sufficient to cause said ethylenically unsaturated starch to copolymerize with said ethylenically unsaturated monomer; and thereby provide a preformed starch copolymerizate article thereof.     
     
     
       25. The method according to claim 24 wherein the appendant ethylenic unsaturation D.S. is less than 0.5, and the starch composition contains 100 parts by weight ethylenically unsaturated starch, at least 10 to about 10,000 parts by weight water and from about 10 to about 2000 parts by weight ethylenically unsaturated monomer. 
     
     
       26. The method according to claim 25 wherein the water-dispersible, ethylenically unsaturated starch comprises a starch represented by the formula: ##STR12## wherein Z represents a divalent organo group linking the terminal ethylenically unsaturated group to the starch chain, starch represents a starch chain, "a" represents a D.S. of greater than 0.05 and "R" is a member selected from the group consisting of hydrogen and a mono-organic group. 
     
     
       27. The method according to claim 26 wherein the ethylenically unsaturated monomer provide a polymer having an average glass transition temperature of less than 70° C. when said monomer is polymerized, and the starch composition contains latent polymerization initiator in an about sufficient to copolymerize said ethylenically unsaturated starch with said ethylenically unsaturated monomer when said starch composition is exposed to polymerization initiating means to cause the copolymerization of said preformed starch composition article. 
     
     
       28. The method according to claim 27 wherein the starch composition has a Brookfield viscosity ranging from about 20 cps to about 5000 cps, a water content ranging from 25 to less than 50% by weight of the total starch composition weight and the starch composition is preformed into a starch composition article by coating a substrate with said starch composition. 
     
     
       29. The method according to claim 25 wherein the preformed starch composition contains at least one effective member selected from the group consisting of film-forming additive, a cross-linking reagent and polyethylenically unsaturated compound with said member being present in said preformed starch composition in an amount sufficient to improve the water-resistance properties of said starch copolymerizate article. 
     
     
       30. The method according to claim 24 wherein the ethylenically unsaturated starch consists essentially of a starch acrylamide represented by the formula: ##STR13## wherein starch represents a starch chain, R 1  is a member selected from the group consisting of hydrogen and a mono-organo group joined directly to the nitrogen atom by a monovalent bond, R represents a member selected from the group consisting of hydrogen and mono-organo group linked to the alpha carbon atom of the ethylenically unsaturated group of the acrylamide moiety by a monovalent linkage, Q represents an organo group which divalently joins the D group with the acrylamide group; D is a member selected from the group consisting of sulfur and oxygen linking said Q group to the starch chain and "a" represents the number of acrylamide substituents per anhydroglucose unit of starch molecule. 
     
     
       31. The method according to claim 30 wherein "a" represents a D.S. ranging from about 0.01 to about 0.3, "R" and "R 1  " represent a member selected from the group consisting of hydrogen, and lower alkyl group and the individual appendant groups are characterized as having a molecular weight greater than 50 but less than 300. 
     
     
       32. The method according to claim 31 wherein the preformed starch composition contains from about 50 to about 500 parts by weight ethylenically unsaturated monomer for each 100 parts by weight unsaturated starch, and D is an oxy group. 
     
     
       33. The method according to claim 32 wherein the ethylenically unsaturated monomer comprise hydroxyalkyl acrylate and Q is a methylene group. 
     
     
       34. The method according to claim 33 wherein the preformed starch composition article contains hydrogen peroxide in an amount sufficient to permit the starch composition to copolymerize and the copolymerization thereof is initiated by subjecting the preformed composition to polymerization initiating means sufficient to cause said hydrogen peroxide to generate free-radicals and thereby copolymerize said starch composition. 
     
     
       35. The method according to claim 34 wherein the starch acrylamide consists essentially of starch acrylamide hydrolyzate and the viscosity of said starch composition ranges from about 20 cps to about 300 cps. 
     
     
       36. The method according to claim 32 wherein the starch composition contains a cross-linking reagent in an amount sufficient to improve the detergent-resistance properties to said copolymerizate. 
     
     
       37. A preformed, non-linear, homogeneous starch copolymerizate article, said starch copolymerizate article comprising the copolymerization product of: (a) water-dispersible, ethylenically unsaturated starch comprised of starch chains and appendant ethylenically unsaturated groups uniformly distributed throughout the starch with said appendant groups being individual monomeric condensates contiguously attached to starch chains at a degree of substitution of at least 0.001; and   (b) water-dispersible, monoethylenically unsaturated monomer homogeneously dispersed throughout the starch in an amount sufficient to copolymerize with the ethylenically unsaturated appendant groups of the starch, with said copolymerizate article being further characterized as being comprised of a labyrinth of starch chains wherein a plurality of the copolymerized appendant ethylenically unsaturated groups of a starch chain molecule are randomly inter-connected to a plurality of copolymerized ethylenically unsaturated groups of starch chain molecules by intervening linkages of said copolymerized monoethylenically unsaturated monomer.     
     
     
       38. The starch copolymerizate article according to claim 37 wherein the D.S. of the appendant group ranges from about 0.02 to about 0.3, and the monomer provide a polymer having an average polymer glass transition temperature of less than 80° C. when said monomer is polymerized. 
     
     
       39. The starch copolymerizate article according to claim 38 wherein the article contains at least one member selected from the group consisting of film-forming additive, cross-linking reagent and copolymerized non-starch, polyunsaturated compound in an amount sufficient to improve the detergent-resistance of said copolymerizate article. 
     
     
       40. The starch copolymerizate article according to claim 37 wherein the ethylenically unsaturated starch contains starch moieties represented by the formula: ##STR14## wherein Z represents a divalent organo grouping linking the copolymerized ethylenically unsaturated moiety to the starch chain, R is an organo group monovalently linked to the alpha carbon atom of the copolymerized ethylenically unsaturated group and "a" represents a D.S. ranging from 0.01 to about 0.5. 
     
     
       41. The starch copolymerizate article according to claim 40 wherein the copolymerized ethylenically unsaturated monomer comprise hydroxyalkyl ester of an alpha, beta-ethylenically unsaturated carboxylic acid. 
     
     
       42. The article according to claim 41 wherein the article contains from about 50 to about 500 parts by weight copolymerized ethylenically unsaturated monomer for each 100 parts by weight copolymerized ethylenically unsaturated starch. 
     
     
       43. The starch compolymerizate article according to claim 42 wherein the copolymerizate is cross-linked with condensation cross-linking reagents in an amount of at least 10% by weight of the total copolymerized ethylenically unsaturated starch and ethylenically unsaturated monomer weight. 
     
     
       44. The starch copolymerizate according to claim 40 wherein Z comprises: ##STR15## moiety with R 1  comprising a monovalent organo group or hydrogen. 
     
     
       45. The starch copolymerizate article according to claim 44 wherein R 1  is a member selected from the group consisting of hydrogen and lower alkyl group of 1 to 5 carbon atoms, and the ethylenically unsaturated monomer comprises hydroxyalkyl acrylate having an alkyl group containing from 2 to 4 carbon atoms inclusive. 
     
     
       46. The starch copolymerizate article according to claim 45 wherein the copolymerizate article comprises from about 100 to about 500 parts by weight copolymerized ethylenically unsaturated monomer for each 100 parts by weight copolymerized ethylenically unsaturated starch and "a" represents a D.S. ranging from about 0.02 to about 0.3. 
     
     
       47. The article according to claim 46 wherein the copolymerizate is cross-linked with condensation cross-linking reagent in an amount sufficient to impart detergent-resistance properties to said starch copolymerizate article.